Scientists have long suspected that poorer neighborhoods are disproportionately afflicted by bed bugs. But since most bedbug data is self-reported, they couldn’t be sure.

So they turned to third-party numbers instead — and found associations between social inequality and bed bug infestations.

In a new study published in People and Nature, researchers from the University of Massachusetts at Amherst and the University of Illinois at Urbana-Champaign found a higher prevalence of bed bug infestations in neighborhoods with lower incomes, higher eviction rates and crowding.

They relied on housing code inspection data from Chicago, where bed bug numbers began to rise in the early 2000s. The Chicago Department of Buildings conducts annual inspections for multifamily units four stories or higher, and inspectors are required to report on pests such as the brown-colored bugs. The insects feed on human blood. They cause rashes and are associated with psychological effects, such as anxiety, sleep disturbances and depression.

The researchers looked at data from over 56,000 inspections that took place between 2006 and 2018, uncovering 491 bed bug infestations. They found that low neighborhood median household income, high eviction rate and high overcrowding all predicted bed bug infestations. All other things being equal, a low-income household was 8 to 12 times more likely to have a bed bug infestation than a high-income household.

The neighborhoods in question are also more likely to face other public health challenges — water contamination, high prevalence of asthma and other chronic health conditions. And, the researchers note, tenants are often blamed for infestations and evicted if they cannot eradicate them. But poverty means less money for pest control, fueling a cycle of disadvantage and continued bed bug infestation.

The findings “provide empirical support for the argument that the contemporary bed bug crisis is an issue of social justice,” they conclude. Rather than pinning infestations on people with low incomes, the study points to ways in which social inequities fuel them — and suggests reforms that tackle poverty, eviction and overcrowding could alleviate bed bug outbreaks, too.